FAIRBORN, Ohio — Awareness and detection of carbon monoxide threats have helped increase the number of incident reports involving the dangerous gas, whose threat rises in the colder months.

The increase has been significant. Americans called fire departments for carbon monoxide incidents an estimated 80,100 times in 2010, according to the National Fire Protection Association.

That was nearly double the 40,900 reports in 2003.

Officials said residents are learning signs of carbon monoxide issues and more are using carbon monoxide detectors, which are encouraging signs.

They also warn that improvements to home construction and maintenance, intended to keep cold air out, also keep gasses in.

Those threats rise beginning this month. The five-month period from October through February accounted for 60 percent of carbon monoxide incidents nationwide in 2010 as more residents seal up their homes and use alternative heating methods. The colorless, odorless, tasteless gas is produced by fuel-burning devices and can be deadly in excess.

"People don't realize homes are less ventilated than they used to be," said Rich Palmer, assistant chief of the State Fire Marshal's Fire Prevention Bureau.

"It's tighter now, with more energy-efficient windows and tightly sealed doors keeping the heat in. Our homes don't breathe like they used to. The modern home is more comfortable, but it stores those gasses."

Officials encourage residents to call the fire department if they suspect a carbon monoxide issue. Firefighters can then use equipment to search for trouble signs, aid in ventilating the home and help contact a utilities provider to work on fixing issues.

Carbon monoxide threats can include gas furnaces or water heaters, fireplaces, charcoal grills or lawnmowers, snowblowers and vehicles that burn gas. It can overcome residents and is potentially fatal.

Experts say homes should include a carbon monoxide detector on each floor. Unlike smoke detectors, which are placed on ceilings, carbon monoxide detectors can sit at any level.

"We need to get people thinking about installing (detectors)," said Judy Comoletti, division manager for public education at the NFPA. "Years ago, you never read about it, and now I think more people know what's happening."

Some fire departments help with that effort. The Fairborn Fire Department, for example, offers a program providing smoke and carbon monoxide detectors it purchases with donated funds to homes, particularly those where small children or seniors live. The six-year-old program has provided several hundred detectors, said Fairborn fire Chief Mike Riley.

Riley said residents should have fuel-burning equipment checked by technicians before the winter and be alert for other potential threats.

"Between last season and this season, a bird could've built a nest in an exhaust flue," Riley said. "There are all kinds of things that can be dangerous."

Some have taken action. A new Residential Building Code of Ohio that took effect this summer requires carbon monoxide detectors to be installed outside of each bedroom or sleeping area in new homes with fuel-burning appliances or attached garages.

While some say they are encouraged by such changes, they want more homes to contain detectors, especially during the months when more residents are staying inside.

"This can build up over time, and there are times of the year when people don't leave the house as much," Palmer said. "If it's a winter weekend, someone might go two or three days without doing much more than checking the mail. It's important for them to be aware of the dangers."